1. Field of the Invention
This invention relates to compositions useful as adhesives and more particularly to the preparation of epoxy-based adhesive compositions with improved impact resistance and/or good adhesion to oily metal substrates.
2. Brief Discussion of the Related Art
Numerous compositions and processes are described in the art for making and using a wide variety of epoxy-based compositions and other resins and additives in an effort to improve the expansion, impact resistance and other key properties of adhesives useful in adhering, filling and making composite structures. For example, patents which describe components for the formulation of adhesive compositions and the use of such compositions to adhere various substrates to each other and to provide structural reinforcement include U.S. Pat. Nos. 5,290,857, 5,686,509, 5,334,654, 6,015,865, 5,278,257, 6,884,854, and 6,776,869 and U.S. Patent Application Publication No. 2005-0022929. Nevertheless, significant problems remain with respect to the preparation of high impact epoxy-based adhesives such as poor retention of peel strength and impact peel performance at low temperatures and poor adhesion to oily metal surfaces.